Pullovers are excellent, either bent arm or straight with a BB or DB. I prefer bent arm versions with DB's because of less stress on the wrist and elbows. In any event the pullover is a great mass builder but also hit's the pec's, triceps and ab's very strongly. By adding the press off the chest after each rep of pullovers (bent are version) your insuring even greater muscle building qualities.
With due respect to Hedgehog, if your so concerned about a disc problem than I wouldn't do bentover rows for a while but I would include hyperextensions in higher (20 or so), lighter reps. Being sure not to go beyond a parrallel position (even with the body). You do not want to overextend the lower back area. I would also warm-up the lower back area with light GM'ing for 20-30 reps or so before training. Might try Hi-pulls, if these don't put too much of a strain on the lower back for you. If your style is correct it should not. Execellent upper back, trap and rear deltoid builder.
Chins are still a great total back builder but some people use the same hand spacing and become bored with it. Might try different grips, which can even be applied in the same workout, doing one set each. Close curl grip, medium, wide, extra wide, behind the neck, Hammer grips, Chin to lower chest, inner locking finger grips, ect. Even muscle up's are a great back builder. If you can work on a pair of gymnastic rings than do so, a superior piece of equipment for all chinning exercises. Good Luck.